Amorphous solids are solids which do not have an crystalline structure. There is no particular order to the make up of these types of solids. When viewed under a microscope or when x-rayed, the molecules that make up the solid are never in the same order from one piece to another.
When amorphous solids break, the pieces tend to be curved or rounded with poorly defined patterns. The distribution of molecules in these types of solids varies from molecule to molecule. Most of the molecules will be a different distance from each other their neighbors. This means that the temperature needed to melt an amorphous solid can vary even through one piece of material.